genetics exam 1

why did Mendel choose pea plant as a model organism?

• well known

• numerous variety

• produce many offspring

• easily grown

• he could readily cross pollinate or self pollinate individual plants

an inherited factor (encoded in the DNA) that helps determine a characteristic

gene

one of two or more alternative forms of a gene

allele

a specific plane on a chromosome occupied by an allele

locus

a set of alleles possessed by an individual organism

genotype

appearance or manifestation of a characteristic

phenotype

when you self pollinate the organism the offspring always produce the same trait(s) as the parent

true breeding

in a heterozygous individual, the two alleles separate with equal probability during gamete formation (each sperm or egg has a 50% chance of receiving either allele)

equal segregation

cross of an F1 (with dominance) to a recessive; allows identification of second allele

tester/back cross

ex. if a plant with flowers that are typically pink or white are crossed, the F1 will have pink and white areas

ex. ABO blood groups and sickle cell anemia (heterozygosity gives resistance to malaria)

co-dominance

ex. a plant with white or red flower produces pink in F1

incomplete dominance

indicates the probability that the difference between the observed and the expected values is due to chance

chi-square goodness of fit test

useful to describe genes and chromosomal abnormalities

specifies the chromosome number, arm (p or q), and region/band

cytogenetic banding notation

during gamete formation, the two alleles of a gene for a particular trait segregate or separate from each other, resulting in each gamete containing only one allele

Law of Segregation

alleles of different genes assort independently of one another during the formation of gametes

Law of Independent Assortment

map genes to specific chromosome locations

DNA

directly visualize which chromosome each gene is on

FISH (fluorescence in situ hybridization)

view chromosome structure

karyotyping

mitochondrial genes are associated with _____

metabolism

chloroplast genes are associated with ____

photosynthesis and carbon fixation

key protein protecting and maintaining mtDNA

TFAM

describe paternal mtDNA elimination

• sperm mitochondria lack intact mtDNA and TFAM

• modified TFAM isoform in spermatogenesis is phosphorylated and directed to sperm nucleus instead of mitochondria

  • TFAM relocalization from sperm mitochondria to nucleus directly correlates with mtDNA elimination, explaining maternal inheritance

T/F: genetic disorders in the mitochondria can only be passed down by the mother

T

when the genotype does not always produce the expected phenotype

incomplete penetrance

individual who carries two different alleles at a locus that result in a recessive phenotype

compound heterozygote

2:1 ratio

recessive lethal allele

sometimes the effect of gene interaction is that one gene masks (hides) the effect of another gene at a different locus

epistasis

in epistasis, the gene that does the masking

epistatic genein

epistasis, the gene whose effect is masked

hypostatic gene

9:3:4 phenotype ratio

recessive epistasis

3:1 ratio

dominant epistasis

9:7 ratio

duplicate recessive epistasis

Where are the ‘hot spots’ for recombination in the human genome?

• G/C rich regions

• methylation

when both dominant alleles are linked on the same chromosome

cis conformationwhe

when the dominant allele is linked to the recessive or mutant allele on the chromosome

trans conformation

degree to which one crossover interferes with additional crossovers in the same region; reduction of expected number of double crossing over events

interference

why are double crossovers rare?

because crossovers are regulated events and interference actively reduces the chance of them occurring nearby

common class of genetic marker based on single base pairs that differ b/w individuals

single nucleotide polymorphisms (SNPs)

relies on huge numbers of variable markers spread throughout the genome; computer seeks out correlations between the markers and the phenotype

GWAS

one of earliest molecular mapping techniques; marker

RFLP